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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"


'                              449

5.  Nature of the Oil.~To ascertain if a Turkey-red oil has beenpre
pared from castor oil or from other oil, or adulterated with mineral oil the
total fat obtained by method 2 (above) is examined.

On this fat the iodine and acetyl numbers are first determined • an
iodine number above 70 and an acetyl number below 140 show immediately
that the oil has not been obtained from pure castor oil. The specific colour
reactions of the different oils (cottonseed, sesame, etc.) may then be tried

It is also to be borne in mind that the emulsive oils prepared with olive'
cottonseed, colza, sesame and similar oils do not usually give clear solutions
with alcohol, as does pure emulsive castor oil.

For detecting mineral or resin oils the saponification test is made.

6.  Ammonia or Soda.—From 7 to 10 grams of the oil are dissolved
ir, a little ether and the solution extracted four successive times with dilute
sulphuric acid (i part of cone, acid and 6 parts of water).   The acid liquids
are then distilled with excess of caustic soda—when ammonium sulphori-
cinate is concerned—and the ammonia absorbed in standard acid; with
sodium sulphoricinate, the acid liquors are evaporated to dryness and the
soda weighed as sulphate.

7.  Iron.—The oil is shaken with dilute sulphuric acid and a few drops
of potassium ferroeyanide solution, ether being then added and the liquid
again shaken and then left to stand.    If iron is present, a more or less interse
blue ring appears at the zone of contact of the two liquids.

# *

Good Turkey-red oils, prepared, from castor oil, usually contain 45-60%
of total fatty substance (the rest being water), but there are more concentrated
types with 85-90% of fat (double oils). Those with about 45% of fat have
the specific gravity .1-0:17-1-035 at 15°. The greater part of the fat consists
of insoluble sulpho-acids and a, small part of soluble sulpho-acids; neutral fat
is present only in small proportion (1-2%). No iron should be present.


(Oleic Acid)

This consists of the liquid fatty acids (mainly oleic acid)—more or less
completely separated from the solid acids—yielded by animal tallow, bone
fat, vegetable tallow, palm oil and other fats. According to its method of
preparation, it is distinguished as okinc oj saponification and distillation
oloine (the latter, unlike the former, usually contains a large proportion
of hydrocarbons resulting from the method of its preparation). In either
case it is a. brownish-yellow or brownish-red liquid, with a peculiar odour,
easily soluble in 85% alcohol, acetic acid or petroleum ether.

The most important determination to be made in commercial oleines
are the following :

1. Acid, Saponification, Ester and Iodine Numbers.—These are
determined by the ordinary methods already described in the preceding
chapter. The ester number, divided by 2, gives the content of neutral fat.
The percentage of free acids (calculated as oleic acid) is usually called the
grade or titcr of the oleine,

A.C,                                                                                                    29             '      (0*070)                            1